1. Technical Field
The present invention relates to saltwater intrusion into fresh water bodies. More specifically, the present invention relates to methods and apparatus for a saltwater intrusion prevention system typically utilized at the interface of a fresh water body with a saltwater body to prevent the incursion of saltwater into the fresh water body.
2. Background Art
The prior art is directed to methods and apparatus for preventing the incursion of saltwater into freshwater bodies.
The intrusion of ocean saltwater into fresh water bodies through man-made structures such as ship channels, drainage channels, and navigation canals typically involves a process by which seawater migrates up-stream into and through the fresh water body. It is noted that seawater has a higher density than fresh water. In the case of a navigation canal, it is noted that the canal can have one or more canal locks that connect the fresh water body with the saltwater body. Each of the canal locks are flooded with water to enable a water craft to travel between the fresh water body at a first elevation and the saltwater body at a second elevation. The terminal ends of each canal lock include lock chamber doors. The seawater migration process occurs when the lower chamber doors of a canal lock are opened to the ocean. Under these conditions, the denser saltwater current displaces the lighter fresh water as it flows into the lock chamber wherein the saltwater is trapped upon closure of the lock chamber doors. This process repeats itself as successive lock chambers are opened and closed during the operation of the canal lock until the seawater has reached the source of fresh water. As a result of this process, the fresh water body insidiously becomes brackish overtime causing significant changes in the ecosystem and creating a serious threat to the water quality of the fresh water body.
In addition to the intrusion of the saltwater into the fresh water body, other problems exist that contribute to the deterioration of fresh water bodies. In tropical regions, annual precipitation is typically high and thus fresh water bodies regenerate during the rainy periods. This ensures that the water level remains relatively high and also serves to reduce pollution in the fresh water body. Often, the fresh water body functions not only as a navigation canal but also supplies water used for farming, public utilities, drinking, bathing and the like. Because of recent global conditions, rainfall levels have fallen off. Further, it is predicted that rainfall levels over the next fifteen years will be unseasonable low. This condition will, of course, result in less water to replenish fresh water bodies. In additional, operation of the canal locks results in a substantial loss of water each time the lock doors are opened and closed. For example, when the lower lock doors are opened to the saltwater body, literally thousands of gallons of fresh water can escape to the saltwater body. This problem is significant since, in some cases, the number of water craft traversing the canal between the fresh water body and the saltwater body is reduced.
Unfortunately, in certain fresh water bodies, portions are dead or dying with vegetation growth. As a result, bacteria feeds on the vegetation reducing the oxygen level in the fresh water body. Further, waste water and chemicals that are injected into the fresh water body increases the bacteria level and this in combination with reduced flow of fresh water destroys the ecosystem resulting in the death of all marine life in the fresh water body. In tropical climates, fresh water bodies normally rise and fall several times annually. This natural flushing serves to minimize the pollution of the fresh water bodies. When there is a large temperature differential between two bodies of water, clouds will form and rainfall is plentiful. For example, the water temperature of the Atlantic Ocean in the Caribbean area (i.e., approximately 85 degrees Fahrenheit) is typically warmer than the water temperature of the Pacific Ocean in the same area. Consequently, annual precipitation is typically plentiful in this geographical area of the world. However, the forecast of lower precipitation levels in the future is based upon the discovery that the water temperatures of the Atlantic and Pacific Oceans are equalizing. This determination has been made based upon the fact that the water temperature of the Pacific Ocean in the Caribbean region is increasing due to volcanic activity on the floor of the Pacific Ocean. Consequently, the level of pollution in fresh water bodies may not be controlled by the natural flushing process in view of the forecast of lower annual precipitation in many areas of the world.
The preceding problems set forth above create a bleak picture for the survival of fresh water bodies. The intrusion of saltwater from the oceans into fresh water bodies converts the fresh water environment into a brackish (ocean salt) environment destroying the natural flora and marine life. The pollution of fresh water bodies also occurs from the injection of waster water and chemicals and the increased growth of vegetation in the fresh water bodies resulting in increased bacteria levels and reduced oxygen levels therein. Additionally, the forecast of lower precipitation levels resulting from the equalizing of the water temperatures of major saltwater bodies, i.e., for example, the Atlantic Ocean and the Pacific Ocean, reduces the likelihood that pollution levels will be controlled by the process of natural flushing. Finally, fresh water is also lost during each operation of the doors of the canal locks.
Thus, there is a need in the art for a saltwater intrusion prevention system typically utilized at the interface of a fresh water body with a saltwater body to (a) increase the supply of fresh water to the fresh water body by employing a lock water recovery subsystem, (b) divert a portion of the water recovered by the lock water recovery subsystem for providing a saltwater intrusion barrier at the interface of the fresh water body and the saltwater body, (c) improve the quality of the fresh water returned to the fresh water body by filtering, aerating and chemically treating the recovered fresh water, and (d) further filter and chemically treat the recovered fresh water at a potable water treatment facility to provide potable water for drinking, bathing, agricultural and utilitarian use.
Briefly, and in general terms, the present invention provides a new and improved saltwater intrusion prevention system for use at an interface between a fresh water body and a saltwater body to prevent saltwater from entering and causing the fresh water body to become brackish. The saltwater intrusion prevention system can be employed where the fresh water body is a navigation canal or ship channel typically associated with canal locks, or a drainage channel interfacing with a saltwater body where canal locks are not present. The saltwater intrusion prevention system is designed to increase the amount of available fresh water in the fresh water body and to arrest the saltwater intrusion into the fresh water body from the saltwater body.
In a preferred embodiment, a canal lock system typically exists which facilitates the transfer of a water craft, i.e., an ocean going ship, a river craft or the like, from the fresh water body to the saltwater body or visa versa. A key feature of the present invention is the capture of the fresh water typically lost, i.e., discharged, from the fresh water body to the saltwater body during the operation of the canal lock system. When the lower lock doors of the existing canal lock are opened, literally thousands of gallons of fresh water, which previously escaped to the saltwater body, are now captured by a water recovery subsystem. The water recovery subsystem taps into the existing culverts of the canal lock system for capturing previously discharged fresh water and routing the recovered fresh water to a fresh water retention reservoir via a lock water recovery culvert and a gate valve. When the retention reservoir is operating, the gate valve is typically in the normally open position so that the recovered fresh water is fed directly into the retention reservoir.
The retention reservoir serves several functions including: (a) delivering a first volume of the recovered fresh water to a saltwater intrusion barrier subsystem located at an interface between the fresh water body and the saltwater body for preventing the intrusion of saltwater into the fresh water body, (b) returning a second volume of the recovered fresh water to the fresh water body to increase the fresh water level thereof; and (c) delivering a third volume of the recovered fresh water to a potable water treatment facility for further processing to provide fresh water to, for example, a local water utility company for drinking, cooking, bathing, agriculture and the like.
The retention reservoir includes a debris screen for filtering out large debris within the recovered fresh water. Once filtered through the debris screen, the first volume of the recovered fresh water is diverted to the saltwater intrusion barrier subsystem via a plurality of weir gate valves, an overflow sump, and a retention reservoir discharge culvert. The retention reservoir discharge culvert terminates in a plurality of submerged return discharge ports positioned to vertically eject the first volume of the recovered fresh water for providing a hydraulic mounding zone. Additionally, a fine air bubbler header comprised of a submerged, perforated, coated pipe is provided for creating a pneumatic mixing zone. The combination of the hydraulic mounding zone and the pneumatic mixing zone serves to increase the density of the fresh water within the interface of the fresh water body and the saltwater body for offsetting saltwater intrusion into the fresh water body.
The remaining recovered fresh water, once filtered through the debris screen, is subjected to a chemical pre-treatment within the retention reservoir to satisfy a first stage treatment standard., This remaining recovered fresh water is also subjected to a course air bubbler header for oxygenating the fresh water. Chemical flocculent is then added to this remaining recovered fresh water for settling suspended solids. The course air bubbler header also serves to mix the chemical flocculent to attach onto the suspended solvents and materials such as oils and grease. A flow baffle is employed for forcing solids to a bottom of the retention reservoir for collection. Thereafter, the second volume of the recovered fresh water is pumped back to the fresh water body to increase the volume of fresh water therein. Finally, the third volume of the recovered fresh water is pumped to the potable water treatment facility for further processing to provide fresh water.
The present invention is generally directed to a saltwater intrusion prevention system typically used at an interface between a fresh water body and a saltwater body to prevent saltwater from entering and causing the fresh water body to become brackish. The saltwater intrusion prevention system can be employed where the fresh water body is a navigation canal or ship channel associated with canal locks, or a drainage channel interfacing with a saltwater body where canal locks are not present. In its most fundamental embodiment, the saltwater intrusion prevention system used at an interface between a fresh water body and a saltwater body includes a water recovery subsystem for recovering fresh water from a fresh water body. A retention reservoir in fluid communication with the water recovery subsystem receives and redirects the recovered fresh water. A saltwater intrusion barrier subsystem in fluid communication with the retention reservoir is positioned at an interface of the fresh water body and the saltwater body. The saltwater intrusion barrier subsystem includes a plurality of submerged return discharge ports for vertically ejecting the recovered fresh water for providing a hydraulic mounding zone, and a fine air bubbler header for creating a mixing zone. The hydraulic mounding zone and the mixing zone increase the density of the fresh water for offsetting saltwater from the saltwater body.
These and other objects and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings which illustrate the invention, by way of example.